I've got an '08 that is also picky with the left saddle bag. It looks like it's closed, but if you give it a decent smack with both palms placed fore and aft on the side, it will close a little further. This satisfies my "open bag" sensor.
Troaf

I've seen quite a few bags end up like this...it is typically caused by overloading the bag and forcing it shut...I don't think there's a lot you will be able to do about it other than remember to give the bag a good push when you shut it.